The proposed research will address the induction of order on solvating water by biological molecules. Our approach is a powerful combination of techniques that will allow a better analysis of this property of biological systems than is achievable with previously used technologies. Our research plan uses the temperature dependence of infrared absorption (TEIR) to directly measure the hydrogen-bonding properties of biological molecules and of the solvent surrounding them. By combining TEIR with a unique variety of solvation conditions, the water-ordering implications of single functional group differences, biomolecular size, and single or double amino acid changes will be described for the first time. The research will focus on neurological small molecule hormones related to depression since these molecules are physiologically very important, provide multiple highly similar molecules with drastically different biological activities, and allow investigation of properties that are applicable to all biological molecules. The proposed research program will provide badly needed insight into this subject.